JP2007159798A - Method and apparatus for measuring skin age - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method for precisely estimating a skin age becoming the index of aging of the skin on the basis of mechanical impedance property, and an apparatus for measuring the skin age. <P>SOLUTION: Compressed air is jetted from a nozzle 7 toward a skin surface (p), deformation of the skin surface in that case is detected by a displacement sensor 8, and a detected value is data-processed by a PC to calculate the mechanical impedance property. Next, on the basis of the elastic item parameter k2 of the mechanical impedance property, the skin age is calculated, or the most approximate age is deduced from a correspondence table. The deduced age is displayed as the skin age. In place of the elastic item parameter k2, a C/K value obtained by normalizing a composite viscosity parameter C with a composite elasticity parameter K can be used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a skin age measurement method and apparatus.

  In recent years, the term skin age is often used in cosmetics-related fields and beauty / health fields such as esthetics as the degree of skin aging, including the presence or absence of wrinkles, stains and dullness on skin, elasticity and moisture retention. It has been broken. There is a need for a method and apparatus that reasonably obtains the skin age.

  As one of the indices for measuring the skin age, measurement methods and apparatuses for measuring elasticity by blowing compressed air on the skin or the like are known. For example, compressed air is instantaneously applied to a measurement surface. The measured displacement of the measurement surface by this spraying is measured with a laser displacement meter, and the measurement result is displayed linearly (see Patent Document 1), or the compressed gas is measured from the injection nozzle Injecting toward the part, measuring the surface displacement of the part to be measured, and evaluating the surface characteristics against the stress of the part to be measured based on the relationship between the time from injection and the surface displacement )

  Further, as proposed by the present inventors, in order to know the deformation characteristics of the surface of the living body such as skin and muscle, an excitation force is applied to the skin and muscle, and the acceleration, speed generated by the excitation force, To measure at least one of the periodic responses of displacement and measure the deformation characteristics of the object based on the transfer characteristics between the excitation force and the response (see Patent Document 3), or to apply the excitation force There is a deformation characteristic measuring apparatus (see Patent Document 4) in which the action point of the air nozzle is aligned with the optical axis of a laser displacement meter that irradiates the action point.

  The one described in Patent Document 1 is an elastic modulus line that is calculated and drawn by a computer based on the advantage that the measurement surface can be measured in a non-contact state and accurate measurement can be performed, and the amount of displacement of the sprayed portion of the compressed air. Is linearly displayed on the display, and there is an advantage that accurate elastic characteristics are determined. However, no method or calculation method for estimating skin age is disclosed.

  In the case of the one described in Patent Document 2, when the compressed air is blown onto the surface to be measured, the surface to be measured is depressed at the maximum displacement, but when the blowing of the compressed air is stopped, the displacement of the depressed portion enters the recovery process, and the displacement is recovered. The skin age is estimated by measuring the required time. For example, the correlation coefficient for age is obtained using parameters such as maximum displacement, time required for displacement, time required for recovery, total time required for recovery, average displacement speed, average recovery speed, etc., and skin age is estimated for parameters with a high correlation coefficient. However, since skin age is estimated by measuring only displacement and time, there is a lack of accuracy.

The devices described in Patent Document 3 and Patent Document 4 grasp the object to be measured as a viscoelastic body, and represent this as a model of a mechanical vibration system using a mass m, a spring k, and a damper c. Each characteristic of c is calculated (see paragraph number 0021 and FIG. 4 of Patent Document 3, paragraph number 0028 of Patent Document 4 and FIG. 9). However, as in Patent Document 1, these documents do not disclose any technique or calculation method for estimating skin age.
If measurement is performed by a contact method using a probe or the like, the collection of measurement data cannot exceed the mechanical response speed of the probe and the actuator that moves the probe. That is, the contact method is not suitable for performing high-speed measurement with a measurement time of 1 second or less.

JP 2003-294598 A JP 2004-108794 A Japanese Patent Laid-Open No. 2004-069668 JP 2005-121614 A

  In view of the above problems, the present invention grasps the skin to be measured as a viscoelastic body and represents it as a model of a mechanical vibration system by a mass m, a spring k, and a damper c, and the mass m, the spring k, A skin age measuring method capable of calculating a mechanical impedance characteristic (each parameter) including a damper c and accurately estimating a skin age as an index of the degree of skin aging based on the mechanical impedance characteristic, and To provide an apparatus.

By injecting compressed air onto the surface to be measured (skin), force is applied in a non-contact manner to deform the surface to be measured. Displacement is measured and measured with a laser displacement meter.
It is assumed that the viscoelastic characteristics of the skin can be estimated from parameters of mechanical impedance characteristics including the mass m, the spring k, and the damper c on the surface to be measured.
From the detection value and the transfer characteristic of the displacement, the mechanical impedance characteristic including the mass m, the spring k, and the damper c on the surface to be measured is calculated by the calculation / control means.

The calculation / control means further estimates the BMI value [body fat percentage = weight (kg) ÷ height (m) ² ], that is, the degree of obesity based on the calculated mechanical impedance characteristic, and calculates the calculated mechanical impedance characteristic. By normalizing the viscosity parameter C with the elastic parameter K in the same characteristic, the viscosity parameter C is corrected with the BMI value as a result. The corrected viscosity parameter C, that is, the C / K value is estimated as the viscoelastic property of the skin.
Then, the age corresponding to the most approximate value is determined as the skin age as compared with the table of age-specific standard values for the C / K values prepared in advance for the viscoelastic properties of the skin.
The determined skin age is displayed as a numerical value by the display means.

  The surface to be measured of the skin to be measured is defined as a parameter in which the spring k and the damper c are coupled in parallel, and further represented by a mechanical impedance characteristic parameter in a model in which two stages are coupled in series. Utilizing this, the mechanical impedance characteristic composed of the mass m, the spring k, and the damper c is calculated. The mass m is small in skin displacement measurement and can be ignored.

  The compressed air for applying a force for measurement is preferably supplied from a sufficiently large air tank via a regulator and a buffer tank. The air tank may be a large tank with a compressor or a small (portable) tank such as a paint spray can.

1. The skin was modeled as a structure in which springs (impedance k) and dampers (impedance c) connected in parallel to the skin surface (each impedance k1, c1, k2, c2) were connected in two stages in series in the thickness direction of the skin. Thus, the displacement response curve as the viscoelastic body estimated from this model is in good agreement with the displacement response curve based on the actual measurement values for the skin, and the skin age can be estimated with high accuracy.
2. Since the value of the elasticity item parameter k2 has the highest correlation coefficient with age, a highly accurate skin age can be calculated.
3. The synthetic elasticity parameter K value has a slightly strong correlation with the physique of the subject. Therefore, the C / K value is a result of correcting the synthetic viscosity parameter C value with the physique. By using the C / K value (corrected viscosity parameter), the skin age can be calculated with high accuracy.
4). Since the C / K value is also a time constant in the step response, it can be easily obtained by measuring the time to reach 63.2% from the displacement response.

5. Since a buffer tank is provided in the compressed air supply path, a stable step-like pressure characteristic can be obtained, and a constant applied force can always be obtained during measurement. Further, the pressure sensor can be omitted. For this reason, the types of data that must be processed by the calculation / control unit are reduced, and a high-performance calculation / control unit is not required. On the other hand, the skin age can be accurately estimated.
6). Since displacement response measurement is non-contact, problems such as damage to the skin and non-hygiene can be solved.

〔apparatus〕
FIG. 1 schematically shows the basic structure of the skin age measuring apparatus 1. This apparatus 1 is of a type in which a hand or arm 3 to be measured is placed on a substrate 2 and a force for measurement is applied by blowing compressed air from above, and is integrated with the substrate 2. A guide 5 is provided on a support column 4 that is constructed upright, and a slider 6 is assembled to the guide 5 so that the position can be adjusted in the vertical direction. The slider 6 includes a nozzle 7 that injects compressed air onto the human skin surface p, and a displacement sensor 8 that measures the displacement of the skin due to the application of force by the principle of triangulation. In the embodiment, the displacement sensor 8 uses a laser displacement sensor LK-030 commercially available from Keyence Corporation.

The nozzle 7 is passed through a cylinder 9 storing compressed air, a regulator 10 for keeping the pressure constant, a buffer tank 11 for storing air at a constant pressure to reduce pressure fluctuation, and an electromagnetic valve 12 for controlling the flow of compressed air. A compressed air supply path 13 is connected.
The skin age measuring device 1 further includes a computing device 14 and a display device 15 connected to its output port. The computing device 14 sends a valve opening / closing signal to the electromagnetic valve 12 while detecting from the displacement sensor 8. A signal is transmitted to the input port.

  The computing device 14 and the display device 15 are constituted by a so-called personal computer. Based on a program for controlling the operation of the entire device in a user-use storage unit and information acquired from the displacement sensor 8, estimation of mechanical impedance characteristics (estimation of each parameter) A program for calculating skin age is stored linked to the OS of the personal computer. Signal transmission to the display device and display data processing depend on the functions of the personal computer.

  As shown in the flowchart of FIG. 2, the measurement procedure is performed by adjusting the slider 6, the distance between the nozzle 7, the displacement sensor 8 and the skin surface p (Example 10 mm), the cylinder pressure (0.6 MPa), and the regulator 10. Adjust or check the pressure adjustment value (0.3MPa) properly by (initialization). Next, when the measurement is started, the program is operated to open the solenoid valve 12 (0.25 sec.), And an applied force f (0.17 N) is applied to the skin by the jet of compressed air from the nozzle 7. (Figure 3). A displacement x of the skin surface p (a dent scale of about 1.5 to 2.0 mm) is measured by the displacement sensor 8. The measured detection value is stored as data in the RAM of the arithmetic unit 14, and based on this data, mechanical impedance characteristics (each parameter) are estimated by a program of a mathematical formula stored in advance, and the mathematical formula stored in the same manner. The skin age is calculated from the corresponding age table. The calculated skin age as a result of the measurement is stored in a RAM as a display buffer and displayed on the display device 15. Appropriate display forms such as numbers, graphs, and pointers can be selected.

In the estimation of the mechanical impedance characteristic, it is necessary to measure the applied force and the displacement of the skin surface p due to this with high accuracy. In this apparatus, the pressure regulator 10 and the buffer tank 11 are provided to obtain a highly reproducible pressure characteristic. Therefore, the mechanical impedance characteristic can be estimated based on the air pressure previously stored in the personal computer after the adjustment without using a pressure sensor that measures the pressure of the compressed air at each injection. In addition, the pressure characteristic at the nozzle position when no measures are usually taken is as shown in FIG. 4 (a), but the pressure characteristic obtained with this apparatus is stepped as shown in FIG. 4 (b). In addition, in the estimation of the mechanical impedance characteristic, the calculation can be performed easily and with high accuracy.
The above means that the arithmetic device may be a processor with low execution speed and memory capacity, and as a result, the cost of the skin age measuring device 1 can be reduced.

[Method 1]
Basic concept Human skin loses its “beam” as it ages. FIG. 5 is a graph obtained by normalizing the displacement data when force is applied to human skin with the maximum displacement, and it returns immediately even if it is depressed in the case of a man in their 20s. It takes time to return. This means that the skin surface p is a surface having viscoelastic properties such as a spring and stickiness, and this property can be understood as changing with aging. The method of the present invention pays attention to this point and measures skin age.

Specific Means For this purpose, compressed air is sprayed onto the skin surface p to apply force without contact, and the displacement response of the skin at this time is acquired without contact. That is, the viscoelastic property of the skin is measured from the applied force and the displacement response of the skin surface p, and the skin age is calculated from the relationship between the skin age stored in advance and the viscoelastic property of the skin. The measurement of the viscoelastic characteristics of the skin is performed by estimating the impedance characteristics (parameters) of the skin viscoelastic model.
When estimating the impedance parameter, as shown in FIGS. 6 (a) and 6 (b), a mechanical impedance model having a spring / damper in which the spring k and the damper c are connected in parallel to each other on the skin surface p in two stages in series. Is used. That is, four parameters k1, c1, k2, and c2 are estimated as mechanical impedance characteristics. k1 and k2 are elastic item parameters, and c1 and c2 are viscosity item parameters.

  This model is a two-degree-of-freedom motion and is represented by the following equation of motion.

さらに（Ｉ）式を印加力ｆと全体の変位ｘとの運動方程式に変形すると

Furthermore, when equation (I) is transformed into a motion equation of applied force f and overall displacement x,

となる、なお、係数はそれぞれ

In addition, each coefficient is

である。

It is.

  Although the applied force f and the displacement x are known data, it is considered that noise is included in the measurement data. Therefore, when the data is differentiated and handled, the accuracy is extremely lowered. In this method, in order to avoid this influence, the equation (2) is transformed into an integral equation that does not show differentiation.

これを行列で表示すると

If you display this as a matrix

ただし

However,

である。

It is.

f and x are measurement data, respectively, according to time series

と表される。
これより、

It is expressed.
Than this,

でインピーダンスパラメーターｚを推定することができる。
ただし

The impedance parameter z can be estimated with
However,

である。

It is.

  Table 1 shows the result of estimating each parameter of the mechanical impedance by this method. Comparing 20's and 50's, it can be seen that there is no significant difference in k1, but there are significant differences in k2, c1, c2.

インピーダンス推定結果

Impedance estimation result

  FIGS. 7A to 7D show the relationship between the age for 67 subjects and the four parameters kl, k2, c1, and c2. Table 2 shows the correlation coefficient between each parameter and age at that time. Among these, when the correlation coefficient −0.632 with the elasticity item k2 is obtained by a method of applying a force to the conventional skin and deforming it, and handling the time from the removal of the force until the deformation is recovered, This correlation is considerably higher than that of the correlation coefficient with age of about 0.561, and it can be said that accurate skin age measurement is possible.

粘弾性パラメーターと年齢との相関係数
なお、年齢の算出は、次式によっても良いし、あらかじめ粘性項目パラメーターｋ２と年齢を対応させたテーブルから近似のものを抽出してもよい。
肌年齢＝６６６５．３×（ｃ/ｋ）＋１２．１６４

Correlation coefficient between viscoelastic parameter and age The age may be calculated by the following equation, or an approximate one may be extracted from a table in which the viscosity item parameter k2 is associated with age in advance.
Skin age = 6665.3 × (c / k) +12.164

  This high accuracy was obtained in the conventional method of time to recovery, while measuring only two pieces of information, “time excluding force” and “time when displacement was recovered”. In the method according to the present invention, how the skin changes, for example, the displacement response of the skin to a force such as a rapid displacement or a slow change, the skin surface p is regarded as viscoelasticity, This is probably because the relationship with age can be expressed well by using impedance characteristics (parameters).

As in this embodiment, when the force is applied with compressed air, the application can be performed at a very high speed. Further, there is an advantage that the force application characteristics can be easily changed by appropriately adjusting the pressure and flow rate of the compressed air. Furthermore, as described above, since the pressure characteristic of the applied air of the skin age apparatus according to the present invention is stepped, the measurement data is stabilized.
In the embodiment, compressed air is used for applying force, but other gases that do not cause any special trouble even when sprayed on human skin may be used, and are generally compressed gases.

[Method 2]
The synthetic viscosity parameter C and synthetic elasticity parameter K of the four-element model of FIG. 6B used in the method 1 can be obtained as follows.
C = c1 · c2 (c1 + c2)
K = k1 · k2 (k1 + k2)
Table 3 shows the correlation between the synthetic viscosity parameter C, the synthetic elasticity parameter K, and the value C / K obtained by normalizing the parameter C with the parameter K and the age of the subject.

Ｃ／Ｋ値と年齢との関係

Relationship between C / K value and age

  Although there is no correlation with age in the synthetic elasticity parameter K, when the correlation with the physique of the subject is taken, the correlation diagram of FIG. 8 is obtained, and a slightly strong correlation with a correlation coefficient of −0.344 appears. Therefore, it can be said that the synthetic elastic parameter K has information on the physique, and the C / K value obtained by normalizing the synthetic viscosity parameter C with the synthetic elastic parameter K corrects the synthetic viscosity parameter C with the physique. As a result, as shown in Table 3 and FIG. 9, there is a high correlation between the C / K value and the age. Therefore, in method 2, instead of the viscosity item parameter k2 in the case of method 1, the C / K value is used for calculation of skin age. The correlation coefficient with age being 0.609 indicates that the correlation between C / K value and age is quite high, and it can be said that accurate skin age measurement is possible even with this method.

Schematic diagram of skin age measuring device schematically shown Flow diagram showing skin age measurement procedure Perspective view of displacement sensor and nozzle part Pressure waveform of compressed air at the nozzle tip, conventional example Pressure waveform of compressed air at nozzle tip, invention of the present application Graph that normalizes displacement data when applying force to human skin with maximum displacement (A) Four-element model shown in skin model (b) Four-element model of mechanical impedance Graph showing the relationship between age and parameters of 67 subjects Graph showing the relationship between age and parameters of 67 subjects Graph showing the relationship between age and parameters of 67 subjects Graph showing the relationship between age and parameters of 67 subjects Graph showing the relationship between the synthetic elastic parameter K and the body mass index BMI Graph showing the relationship between C / K and age

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Skin age measuring device 2 Board | substrate 3 Object to be measured 4 Support | pillar 5 Guide 6 Slider 7 Nozzle 8 Displacement sensor 9 Cylinder 10 Regulator 11 Buffer tank 12 Electromagnetic valve 13 Compressed air supply path 14 Computation device 15 Display device

Claims (7)

  The skin to be measured is connected to the skin surface in parallel with springs (impedance k) and dampers (impedance c) (each impedance k1, c1, k2, c2) in series in the skin thickness direction. It is regarded as a four-element model having a structure, a compressed gas is sprayed onto the surface to be measured of the skin, a force is applied to the skin in a non-contact manner, and a transfer characteristic between the applied force (f) and the displacement (x) The mechanical impedance characteristic is calculated, and the value of the elastic item parameter k2 of the mechanical impedance characteristic is set as the viscoelastic characteristic of the skin on the surface to be measured, which is compared with the standard value by age regarding the parameter k2 prepared in advance, and is the most approximate A method for measuring skin age, wherein the age corresponding to the value to be determined is defined as skin age.   The skin to be measured is connected to the skin surface in parallel with springs (impedance k) and dampers (impedance c) (each impedance k1, c1, k2, c2) in series in the skin thickness direction. Considering a four-element model with a structure, injecting a compressed gas onto the measurement surface of the skin to be measured, applying force to the skin in a non-contact manner, measuring the displacement of the measurement surface by the applied force, The mechanical impedance characteristic on the surface to be measured is calculated from the transmission characteristic between the applied force (f) and the displacement (x), and the resultant viscosity parameter C (c1 · c2 / (c1 + c2)) is combined with another mechanical impedance characteristic. The corrected viscosity parameter C / K corrected with the BMI value is obtained by normalizing with the elasticity parameter K (k1 · k2 / (k1 + k2)), and the C / K value is obtained as the viscoelasticity of the skin at the measurement site. The skin age is characterized in that the age corresponding to the most approximate value is used as the skin age by estimating the sex and then comparing the C / K value with the standard value by age relating to the C / K value prepared in advance. .   The skin according to claim 1 or 2, wherein the compressed gas sprayed to the surface to be measured has a step-like pressure for a short time in which the force applied to the skin is maintained substantially constant. Age measurement method. Force application means for applying force in a non-contact manner by injecting compressed air continuously or in a pulsed manner onto the measurement surface of the skin to be measured;
A pneumatic control means for changing the amplitude, vibration frequency or duty ratio of the compressed air of the force application means;
A measuring means comprising a laser displacement meter for measuring the displacement caused by the excitation force applied to the surface to be measured;
From the transmission characteristic between the applied force from the force applying means and the displacement of the measured surface, a mechanical impedance characteristic composed of the mass m, the spring k, and the damper c on the measured surface is calculated, and the calculated mechanical inbee The BMI value (body fat percentage), which is an index of obesity, is estimated from the elastic parameter k in the dance characteristic, and then the viscosity parameter c in the machine impedance characteristic is normalized by the elastic parameter k, and the skin is expressed by the BMI value. Calculation / control means for correcting and estimating age,
Display means for displaying the skin age estimated by the calculation / control means numerically;
An apparatus for measuring skin age, comprising:   The calculation / control means represents the surface to be measured of the skin to be measured as a model in which a spring k and a damper c are connected in parallel and connected in two stages in series, and the mass m is calculated using the model. The skin age measuring apparatus according to claim 4, wherein each mechanical impedance characteristic comprising a spring k and a damper c is calculated. A gas ejection device including a nozzle, a laser displacement measurement device, a control / calculation device, and a display device are provided, and the gas ejection device is arranged with the nozzle close to a measurement surface selected for the skin to be measured. The nozzle is connected to a constant pressure gas supply path equipped with a solenoid valve, and the laser displacement measuring device detects the amount of skin displacement on the surface to be measured and transmits it to the control / calculation device. The control / calculation device opens and closes the solenoid valve at a set time, and captures the synchronized pressure of the constant pressure gas to the skin (f) and the “open” state of the solenoid valve from the laser measuring device. The calculation function of estimating the mechanical impedance by calculating the following mathematical formula based on the four-element model from the detected displacement (x) of the skin, and the mechanical impedance of the estimated four elements One of the parameters selected from the parameters is used as the viscoelastic property of the skin on the measurement surface, and the age corresponding to the closest parameter value is compared with the age correspondence table stored in advance corresponding to the selected parameter. A skin age measuring device comprising a calculation function for selecting and displaying a selected corresponding age on a display device.

The skin age measuring apparatus according to claim 6, wherein the constant pressure gas supply path including the electromagnetic valve is connected to the electromagnetic valve from a compressed gas source through a pressure regulator and a buffer tank.

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